Room wall thermostat

ABSTRACT

A wall thermostat comprises a molded panel frame attachable to a room wall. A switch mechanism and a plate type bimetal are supported on opposite sides of the panel with operating bars between the bimetal and switch. The bimetal is urged against three support points, comprising two spaced abutment surfaces on the frame and an adjusting cam carried by the frame by the reaction of the switch actuating mechanism against the operating bars which engage the bimetal at points inside the triangular area outlined by the three support points. The switch mechanism is supported by abutment surfaces formed on the frame panel by the same mold member which forms the two spaced abutment surfaces.

United States Patent [151 3,668,594 Kulick 1 June 6, 1972 [54] ROOM WALL THERMOSTAT 3,466,587 9/1969 Rechou et al ..337/379 [72] Inventor: Andrew Kulick, Columbus, Ohio Primary Examiner Be'mard A. Gflheany [73] Assignee: Ranco Incorporated, Columbus, Ohio Assistant Examiner-Dewitt M. Morgan [22] Filed Oct 21 1970 Attorney-Watts, Hoffman, Fisher & Heinke [52] US. Cl ..337/380, 337/360, 337/377 [51] Int. Cl "HOlh 37/14, HOlh 37/20, HOlh 32/52 [58] Field of Search ..337/42, 102, 111, 333,334,

[56] References Cited UNITED STATES PATENTS 3,421,131 1/1969 Moyer et al ..337/338 3,553,624 1/1971 Dalzell et a]. ...337/102 X 2,888,537 5/1959 Mears ..337/338 3,454,919 7/1969 Kulick ..337/360 3,463,008 8/1969 Teichert et al ..337/3 80 UX Appl. No.: 82,767

ABSTRACT A wall thermostat comprises a molded panel frame attachable to a room wall. A switch mechanism and a plate type bimetal are supported on opposite sides of the panel with operating bars between the bimetal and switch. The bimetal is urged against three support points, comprising two spaced abutment surfaces on the frame and an adjusting cam carried by the frame by the reaction of the switch actuating mechanism against the operating barswhich engage the bimetal at points inside the triangular area outlined by the three support points. The switch mechanism is supported by abutment surfaces formed on the frame panel by the same mold member which forms the two spaced abutment surfaces.

4 Claims, 10 Drawing Figures PATENTEDJUH 5 I972 3, 668 594 SHEET 10F 4 INVENTOR ANDREW KUL/CK BY ATTORNEYS PATENTEDJUR 6 E97? 3, 668 594 HIIIH x i D2 t;

a a l? INVENTOR. ANDRE W KUL/CK z/Q jaw/M ATTORNEYS PATENTEDJUN s [972 INVENTOR. ANDREW KUL/CK A 7'7'ORNE Y5 ROOM WALL THERMOSTAT BACKGROUND OF THE INVENTION The present invention relates to wall type thermostats of the type comprising a bimetal member which actuates an electric control switch and arranged so that heat generated by the passage of current through the switch is carried away by air flow between the switch and bimetal. Thermostats of the type mentioned generally comprise a panel-like frame which may be conveniently attached to an outlet junction boxin the wall ofa room, for example. The frame has a switch supported on one side and a bimetal element supported on the opposite side. The bimetal and switch are interconnected so that movements of the bimetal in responding to temperature changes operate the switch. Usually, means are provided for varying the spatial relationship of the bimetal with the switch so as to vary the range of temperatures at which the switch is operated by the bimetal. Because of the minute movements involved between the bimetal and switch, close tolerances of certain parts of the thennostats are required and result in relatively costly constructions. An example of the type of wall room thermostat referred to is disclosed in U.S. Pat. No. 3,454,919.

THE PRESENT INVENTION The present invention provides a room thermostat of the type mentioned which can be easily assembled with a minimum of parts and yet provide an accurate, durable and highly serviceable thermostat. The invention contemplates the provision of a panel-like frame which can be manufactured of a single molded member formed in such a manner that one end of the bimetal may be shaped to nest into two spaced support abutments integral with the frame and the opposite end of the bimetal has a point bearing engaging an adjusting cam on the frame, the bimetal being retained in engagement with the abutments and cam by a resilient force exerted by the switch actuating mechanism of the switch attached to the frame, the force being transmitted through a bar or link engaging the bimetal at a point lying within a triangular area outlined by the portions of the bimetal engaging the two support abutments and the point connection of the bimetal with the cam. The switch mechanism includes 'a casing attached to the panel by clamps urging portions of the casing to abutment surfaces fonned integral with the frame and by the same mold member which forms the two abutments engaged by the bimetal whereby accurate spacing of the bimetal and switch is assured with a minimum of attention to these dimensions during manufacture of the thermostat.

Other objects and advantages of the invention will be apparent from the following description of a preferred form thereof, reference being made to the accompanying drawings wherein:

FIG. 1 is a front elevational view of a thermostat embodying the invention and shown attached to a wall of a room;

FIG. 2 is a sectional view of the thermostat with the cover removed and taken substantially along line 2-2 of FIG. 1;

FIG. 3 is a front elevational view of the frame of the thermostat having the switch mechanism assembled thereto;

FIG. 4 is an end elevational view of the thermostatic frame and switch shown in FIG. 3 and the cover is shown spaced from the frame;

FIG. 5 is a side elevational view of the frame and switch shown in FIG. 3;

FIG. 6 is a sectional view of the frame and switch taken substantially along line 66 of FIG. 3;

FIG. 7 is a sectional view taken substantially along line 7-7 of FIG. 6;

FIG. 8 is a sectional view taken substantially along line 8-8 of FIG. 7;

FIG. 9 is a sectional view taken along 9-9 of FIG. 8; and

FIG. I0 is a sectional view taken substantially along line 10-10 of FIG. 2.

Referring particularly to FIGS. 1 and 2, a room thermostat 10 is shown which is particularly suitable for controlling the flow of current to electric heating elements located in a room to be heated. The room and heating elements are not shown as they are well known in the art. In general, thermostat 10 comprises a frame 11 which may be conveniently attached by suitable fasteners to the junction box B inset in the room wall W. An electric snap switch mechanism 13 is carried on one side of the frame 11 and is disposed at least partially inside the junction box. The switch mechanism 13 includes a pair of snap switches operated by the deflection of a bimetal plate I4 supported on the opposite side of the frame in response to changes in the temperature of room air moving thereabout. The bimetal 14 is operatively connected with the switch mechanism 13 by a pair of bars or push rods 15,16. The lower end of the bimetal 14 is fixedly supported on the frame 11 and the upper end may be shifted towards and from the switch mechanism 13 by a rotatable cam 17 to change the temperatures at which the snap switches are operated. The side of the frame 11 supporting the bimetal 14 has a cover 18 which shields the bimetal and permits access to a temperature setting adjustment knob 20 which is integral with the cam 17 for adjustment thereof.

The frame 11 is preferably formed of a molded material, such as a suitable thermosetting plastic, and includes a face or main panel 23 having rearwardly extending top, bottom and side flanges 24,25,26,27 respectively. The top and bottom flanges 24 and 25 each has a pair of notches or recesses 28 formed therein to provide for a vertical air flow through the frame, as is explained hereinafter. The outer edges of the flanges 24-27, excluding the recessed portions of the flanges 24,25, lie in a common plane and are adapted to lie against the surfaces of the wall W about the recessed junction box B.

The frame 11 is attached to the junction box B by two screws 30, 30' which extend through oval openings 31,32 in two recessed portions of the panel 23. The heads of the screws 30,30 are received in the recesses as is shown best in FIG. 2.

The switching mechanism 13 comprises a plastic, molded box-like housing 35 having a rectangular open side. The housing is divided into two compartments by a partition 36 and snap switches 37,38 are located in the respective compartments. The open side of the housing 35 is closed by a cover panel 41, the edges of which rest on an inset shoulder 42 around the open side of the housing.

' The snap switches 37,38 are alike in construction and for sake of brevity, only switch 38 is described in detail; however, like parts of switch 37 bear the same reference numerals with a prime added. Referring to FIGS. 8 and 9, the switch 38 comprises a cantilever supported spring blade 44, one end of which is suitably attached to the inner surface of a support member 45 and the opposite end of which is adapted to shift between a stop 46 and a fixed contact 47. The stop 46 comprises a boss formed on the wall of the housing. The last mentioned end of the blade 44 has a contact 48 secured thereto which is adapted to engage the contact 47 when the blade is urged towards the fixed contact. The central portion of the blade 44 is cut out to form a tongue 50, the base of which is integral with the shiftable end of the blade. The end of the tongue 50 remote from its base is secured in a notch in a lug 51 formed on an arm of the blade support member 45. The tongue 50 is attached to the lug 51 with the tongue bowed and in compression and so that it serves to urge the free end of the blade to either the stop 46 or to the contact 47, depending upon what side of the tongue the centerline of the blade 44 may be. The blade 44 is formed to normally flex towards the contact 47 so that the tongue normally urges the blade to close contact 48 on contact 47. The blade 44 is adapted to be shifted and cause its centerline to move to the other side of the connection between the tongue 50 and lug 51 by the operating bar 16. This causes the blade to separate the contacts 47,48. The bar 16 is moved to open the switch by deflection of the bimetal 14. In any event, the blade 44 continually urges the bar 16 against the bimetal 14 when the bimetal is assembled to the frame 1 l.

The operations of the switches 37,38 in response to longitudinal movements of their operating bars 15,16 can be varied by bending the lugs 51,51 towards or from the blades 44,44 proper so that the centerlines of the blades pass the dead center positions of thetongues 50,50 with more or less move ments of the operating bars. Preferably, the switches 37,38 are adjusted so that one closes and opens at a lower temperature than the other.

The blade support member 45 comprises a metal stamping generally Z shape, and one end portion is secured to a recessed wall of the housing 35 by a terminal bar 52 which has a portion extending through an opening through the housing wall and staked in an opening through the blade 44. The terminal bar 52 is formed to abut a portion of the outer side of the recessed wall of the housing to firmly position the bar on the housing. A terminal screw 53 is threaded into an opening through the bar 52 and extends into a recess in the outer wall of the housing for receiving a terminal wire connection.

The contact 47 is attached to a terminal support member 54 which is secured to the wall by a terminal bar 55. The bar 55 is like the bar 52 and is staked to the member 54 and secured to a recessed housing wall in the same manner as the bar 52 is secured to the member 45 and the housing wall. A terminal lead wire, not shown, may be attached to the terminal bar 55 bya terminal screw 56 threaded into the bar.

The terminal connections comprising the screw 53 and bar 52, and screw 56 and bar 55 are shielded by three parallel insulating partitions comprising the central partition wall 36 and side walls 57,58, all of which are molded integral with the housing block. The terminal connections effected by the screws 53,56 are adapted to connect the switch 38 in series circuit with a suitable electric power supply and a heater element, not shown.

The switch operating bar 16 extends freely through an opening through the cover 41 and has a pair of neck portions 61, only one of which appears in the drawings, which extend through a pair of openings in the blade 44. The opposite end of the operating bar is similarly attached to the bimetal 14, as described hereinafter. The switch operating bar is similarly connected with the blade 44' of the switch 37 and the bimetal 14. The switch blades 44,44 exert forces against the operating bars 15,16 and continually urge the bars towards the bimetal 14 which retains the bars connected with the respective switch blades and the bimetal. The switches 37,38 operate at different degrees of movements of the operating bars 15,16 so that different banks of electric heaters may be energized according to heating requirements, If desired, one of the switches could be eliminated where a single heater element is to be controlled. r

The housing 35 is attached to the frame 11 in a predetermined spacing relative to the bimetal 14 by abutting four lugs 63 formed on the housing against four abutments 64 formed on the frame. The abutments 64 each has a locating lug 65 at one corner which prevent shifting of the lugs 63 relative to the abutments 64. The housing 35 is secured against the abutments 63 by a pair of mounting plates 66 at two opposite sides of the housing. The mounting plates 66 are generally T shape and the wing portions 67 lie along one edge of the lugs 63. The stem of the plates 66 extends between two of the abutments 64 and a neck portion 68 projects through slot-like openings in the panel 23 of the frame. Opposite side portions of the necks 68 are split and bent outwardly to engage the end edge portions of the slot shaped openings to thereby firmly secure the mounting plates to the frame and exert a pressure urging the housing lugs 63 to the frame abutments 64.

When the switch mechanism 13 is attached to the frame 11 in the manner just described, the switch operating bars 15,16 are each extended through one of a pair of sleeves 70,71 formed on the frame 11. The openings through the sleeves 70 are rectangular in cross section and are of a size such that the sides of the openings do not touch the operating bars. The bars 15,16 project beyond the ends of the sleeves. In assembling the thermostat 10, the switching mechanism is first attached to the frame 11 in the manner just described, after which the bimetal 14 is assembled to the frame.

The bimetal 14 is a generally rectangular plate and the edge portion along one end is turned at right angles, forming a flange 72. Two notches 73,73 are formed at opposite sides of the bimetal adjacent the flange 72. The notches 73,73 permit the bimetal to be manipulated so that the opposite end portions 74,74 of the flange 72 may be inserted into slots 75,75 formed in the outer ends of two support legs 76,76 formed on the frame 11. The support legs 76,76 are molded integral with the frame proper and are generally V shape, and extending from the forwardly facing panel of the frame 11. In forming the legs 76,76 a male mold member has projections which form V-shape recesses 77,77, including the slots 75,75, in the inner sides of the legs. As may be best seen in FIG. 6, which shows the leg 76 in section, the recess 77' opens to the rear face of the panel 23. The same holds true relative to the recess 77. The slots 75,75 are formed at the apexes of the recesses. The legs 76,76 are each reinforced by lateral webs 78,78 which join the outside wall of each leg.

It will be noted that the legs 76,76 are preferably molded by the same male die'member which fonns the surfaces 80 of the abutments 64 against which the lugs 63 of the switching mechanism abut and which locate the switch mechanism 13 relative to the bimetal 14. Thus, the spacings of the abutment surfaces 80 and the inner ends of the slots 75,75 will be inherently of precise and uniform dimensions throughout the manufacture of numerous frame members. This permits accurate spacing of the bimetal and switch during manufacture of quantities of the thermostats.

The bimetal plate 14 is assembled to the frame 11 by canting the bimetal and inserting the end portions 74,74 of the flange 72 into the recesses 77,77 and then nesting these portions in the slots 75,75. The bimetal will then extend generally parallel to the panel 23.

The flanged end of the bimetal is urged in a direction to seat the portions 74,74 thereof against the inner ends of the slots 75,75 by an L-shaped spring member 81. The spring 81 has a foot portion which nests in the recess for the mounting screw opening 32 and which has an opening through which the shank of the mounting screw 30' may extend. The leg portion 82 of the member 81 is biased longitudinally and engages the bimetal 14 to urge the bimetal into the slots 75,75. The outer end of the leg 82 is coupled to the bimetal by a necked end portion extending into a slot'formed in the bimetal. The lower wall of the recess for the opening 32 is recessed to receive the leg 82. When the frame 11 is secured to the junction box B as described, the head of the screw 30 engages the member 81 and provides a ground connection by which the bimetal is grounded through the spring 81.

The bimetal 14 has an opening 83 through which a cam shaft bushing 84, formed on the frame 11, projects when the bimetal is assembled to the legs 76,76, as described. The outer ends of the switch operating bars 15,16 have neck portions 15,16 which project through slots 85,85 through the bimetal. The walls of the slots cooperate with the neck portions of the barsto maintain the ends of the bars to the inner side of the bimetal 14 and to position the bars spaced from the insides of the sleeves 70,71.

The cam 17 is then assembled to the frame 11 so as to be facing the outer side of the bimetal 14. The cam 17 is preferably fonned of a single molded member which includes the drum-shape knob or dial 20 having a helical cam surface on the underside, as viewed in FIG. 1. A shaft 86 is embedded in the knob 20 axially thereof and is joumaled in the bushing 84. The bushing 84 is formed on a protruding, box-like portion 87 of the frame 11. The shaft 86 is secured in the bushing by a split, bowed spring washer 88 engaging an annular shoulder 89 about the shaft and formed by undercutting a portion of the shaft. The rotation of the knob 20 and cam 17 is limited to less than 360 by a lug 90 formed on the underside of the knob and which engages opposite sides of a spline 91 formed on the bushing 84.

The end portion of the bimetal 14 opposite the flanged end has a screw 92 threaded therein on the centerline of the bimetal. The screw 92 is maintained in engagement with the cam 17 by the reaction of the switch operating bars 15,16 against the bimetal, as explained previously. This reaction of the switch blades 44 against the bimetal 14 also retains the bimetal flange portions 74,74 against the closed ends of the slots 75,75 in the two support legs 76,76. An important feature of the invention is the fact that the center of the forces applied to the bimetal 14 by the switch actuating bars 15,16 falls within a triangle defined by the three broken lines 95,96 and 97. Line 95 extends from the center of the area of engagement of the screw 92 with the cam 17 through the center of the support point formed by the flange portion'74 with the inner end of the slot 75. Line 96 extends from the center of the area of engagement of the screw 92 with the cam 17 through the portion 74 of the bimetal flange engaging the inner end of the slot 75'. The line 97 extends along the centerline of the flange 72, the ends of which form the support points for the bimetal 14 at the lower corners thereof. Thus, the forces of the switch actuating bars 15,16 acting on the bimetal 14 always tend to maintain the bimetal in a stable position relative to the frame 11 by forcing the bimetal against three support points. This condition will prevail although only one switch mechanism and operating bar might be employed, in which case the single switch actuating bar would fall within the triangular area out lined by the three bimetal support points.

As the knob 20 is rotated in one direction or the other, the cam 17 shifts the upper end of the bimetal 14 towards or away from the frame 1 1. This requires more or less temperature induced deflection of the bimetal to occur in operating the switches 37,38 through the bars 15,16.

Calibration of the thermostat is effected by adjustment of the screw 92 into or out of the bimetal. The adjustment may be made by a screwdriver through an opening 100 through the frame wall 23.

It is common practice in the art to minimize temperature excursions of the space being heated by slightly heating the bimetal during the heating cycle. In the present instance an electric resistance element 101 is secured to the bimetal 14 by a screw 102. Lead wires 103 are provided for connecting the v resistance element in the switch circuit.

' The frame 11, with the bimetal 14 and switch mechanism 13 assembled thereto, is attached to the junction box B after the switching circuit connections have been made. With the cover 18 removed, the mounting screws 30,30 are readily accessible from the front of the frame. The screw 30 is inserted through an opening 104 through the bimetal. After the frame 11 is secured to the box B, the cover 18 is attached to the frame.

The cover 18 is preferably molded of a suitable plastic and is box-like in form. The open side of the cover is adapted to telescopingly receive the forward portion of the frame and the rear edges of the cover 18 terminate short of the notches 28 in the top and bottom walls of the frame. A detent arrangement frictionally secures the cover to the frame. Because the details of the cover are not essential to the understanding of the invention, the detent structure is not shown. Suffice to say, the face of cover 18 has an opening through which the knob 20 projects. A marker 106 on the knob cooperates with indicia on the cover face about the opening 105 to indicate the temperature setting of the thermostatic device. The cover 18 has air passage openings 107 in the top and bottom walls which permit an upward draft of room air to flow about the bimetal plate supported on the o posite side of said frame and operatively connected nth sai switch mechanism, characterized by said frame comprising a molded member having a bimetal supporting wall section, a pair of spaced support members molded integral with said wall section and projecting from said opposite side of said frame, said support members having recesses formed therein with one end open to said one side of said frame, the inner end walls of said recesses forming support surfaces facing said open ends of said recesses, said bimetal having a pair of spaced parts extending into said recesses and abutting the respective said support surfaces thereof, and means urging said bimetal to tend to maintain said spaced parts in engagement with said support surfaces.

2. A thermostatic control as defined in claim 1 further characterized by said support members having the recesses therein open along one projecting side, said open sides of said recesses facing one another.

3. A thermostatic control as defined in claim 6 further characterized by two opposite walls of each of said recesses converging towards said support surfaces respectively.

4. A thermostatic control as defined in claim 1 further characterized by said frame having abutment surfaces on said one side of said frame and facing in the same direction as said support surfaces in said recesses, locating abutments on said switching mechanism engaging said abutment surfaces, and means for securing said switching mechanism to said frame with said locating abutments engaging said abutment surfaces. 

1. A thermostatic control comprising a panel-like frame, a switch mechanism supported on one side of said frame, a bimetal plate supported on the opposite side of said frame and operatively connected with said switch mechanism, characterized by said frame comprising a molded member having a bimetal supporting wall section, a pair of spaced support members molded integral with said wall section and projecting from said opposite side of said frame, said support members having recesses formed therein with one end open to said one side of said frame, the inner end walls of said recesses forming support surfaces facing said open ends of said recesses, said bimetal having a pair of spaced parts extending into said recesses and abutting the respective said support surfaces thereof, and means urging said bimetal to tend to maintain said spaced parts in engagement with said support surfaces.
 2. A thermostatic control as defined in claim 1 further characterized by said support members having the recesses therein open along one projecting side, said open sides of said recesses facing one another.
 3. A thermostatic control as defined in claim 6 further characterized by two opposite walls of each of said recesses converging towards said support surfaces respectively.
 4. A thermostatic control as defined in claim 1 further characterized by said frame having abutment surfaces on said one side of said frame and facing in the same direction as said support surfaces in said recesses, locating abutments on said switching mechanism engaging said abutment surfaces, and means for securing said switching mechanism to said frame with said locating abutments engaging said abutment surfaces. 